Tell me the Excel formula to categorise donors based on an amount donated, then count how many donors in each category

I have an Excel table, starting in A1, with the following columns: Donor Name, Contact Email, Total Donation Amount
I want to add a new column that will set Donor status to "Major" if they donate over 1000, "Mid" if they donate over 500 and "Mass" if they donate less than 500. What is the formula for this?

Now in a separate sheet I want to calculate how many Major, Mid and Mass donors I have. How would I do this? My original information was in Sheet1.